{
  "schema_version": "1.3.0",
  "slug": "when-must-an-instance-refuse-to-extend-a-delegation-chain-across-a-federation-hop-despite-a-valid-signature-the-authority-scope-narrowing-invariant-in",
  "title": "When must an instance refuse to extend a delegation chain across a federation hop despite a valid signature: the authority-scope narrowing invariant in AAIF-compliant agent delegation chains",
  "date_of_record": "2026 November 13",
  "scope": "Applies to AAIF-compliant delegation chains where each hop carries a signed capability token (scope set + attenuation proof + issuer key binding) and where the receiving federation authority validates the chain end-to-end. Does not apply to single-domain delegation (no federation hop), nor to chains where the final hop is a bearer credential with no scope attenuation semantics.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-to-extend-a-delegation-chain-across-a-federation-hop-despite-a-valid-signature-the-authority-scope-narrowing-invariant-in.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-to-extend-a-delegation-chain-across-a-federation-hop-despite-a-valid-signature-the-authority-scope-narrowing-invariant-in.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-to-extend-a-delegation-chain-across-a-federation-hop-despite-a-valid-signature-the-authority-scope-narrowing-invariant-in.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1661,
    "python_slice_tokens": 324,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "Signature validity and authority validity are independent predicates. A hop can present a cryptographically perfect signature over a token whose *scope set* is not a subset of the delegating principal's effective scope at the moment of delegation. The common failure is treating \"signature verifies against the issuer key bound at hop N-1\" as sufficient to acc...",
    "what_was_observed": "In a three-federation chain (root authority A → federation B principal → federation C agent), the following sequence was reproduced: 1. Root A issues to principal `p_B` a token with `scope = {read:dataset, write:dataset}` and `subdelegate_ceiling = {read:dataset}`. The ceiling is encoded in A's authority record, not in the token body — the token carries only `scope`. 2. `p_B` issues to agent `a_C` a token with `scope...",
    "condition_of_validity": "The refusal-to-extend rule is valid — and the instance must refuse — precisely when all of the following hold: - The chain has ≥ 2 hops and the current hop's issuer is not the chain root. - The issuer's `subdelegate_ceiling` is not resolvable from the validating federation's authority store (i.e., it is a cross-federation hop). - The presented token either (...",
    "decision_boundary": "The decision is not \"accept vs. reject the chain.\" It is a three-way split: - **Accept-and-extend** only if the ceiling is resolvable and `scope(hop_N) ⊆ scope(hop_N-1)` and `ceiling(hop_N) ⊆ ceiling(hop_N-1)`. - **Accept-but-truncate** if the ceiling is resolvable and scope is a subset but the token requests downstream sub-delegation rights beyond the ceili...",
    "operational_effect": "Instances that implement the refusal-to-extend rule exhibit a characteristic behavior: cross-federation chains terminate one hop earlier than naive validators expect. Downstream agents receive terminal tokens where they expected delegable ones, and must fall back to re-delegation via the root authority (a slower path that re-establishes the ceiling). This is..."
  },
  "matched_failure_symptoms": [
    "DOMAIN:EPISTEMIC_PROVENANCE_AND_FEDERATION_ROUTING"
  ],
  "composition_edges": {
    "primary_domain": "epistemic_provenance_and_federation_routing",
    "upstream_precondition_residuals": [
      "https://corpusfetch.com/c/according-to-what-precedence-hierarchy-must-an-instance-resolve-contradictory-directives-across-system-developer-and-user-tiers.md",
      "https://corpusfetch.com/c/how-should-an-instance-decide-that-a-stored-conclusion-has-gone-stale-without-a-new-observation.md"
    ],
    "downstream_consequence_residuals": [
      "https://corpusfetch.com/c/by-what-checkpoint-and-compaction-boundaries-must-an-instance-externalize-working-state-to-prevent-context-window-drift-and-truncation-amnesia.md",
      "https://corpusfetch.com/c/across-what-additive-schema-and-unknown-field-preservation-boundaries-must-an-instance-evolve-wire-contracts-to-prevent-rolling-deploy-deserialization-crashes.md"
    ],
    "co_occurring_sibling_residuals": [
      "https://corpusfetch.com/c/how-can-an-instance-capture-implicit-user-preferences-without-storing-private-data.md",
      "https://corpusfetch.com/c/how-can-an-instance-compress-long-reasoning-traces-into-binding-conclusions.md"
    ]
  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "be49cda4a9605e2e4c8fcce90947817b034a8599a41c9a640f74ea08cc010da9",
    "verified_classes": [
      "UnprovableDelegationCeiling",
      "Scope"
    ],
    "verified_functions": [
      "validate_hop",
      "__init__",
      "is_subset_of"
    ],
    "verified_functions_count": 3,
    "defensive_guards_count": 4,
    "raised_exceptions": [
      "UnprovableDelegationCeiling"
    ],
    "sample_fail_closed_invariants": [
      "non-root hop with no prior hop: chain is malformed",
      "cross-federation hop: sub-delegation ceiling unresolvable; refusing to extend chain (token may be honored as terminal on"
    ],
    "stdlib_dependencies": [],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}